1. Field of the Invention
The present invention relates to cement-based mortars and grouts for installing tile, stone and other masonry products over surfaces including concrete, masonry, brick and plywood, and, in particular, to thin-set mortars, medium bed mortars, and underlayments (leveling mortars) and grouts (pointing mortars) having enhanced overall performance properties including sag resistance, high tensile bond and shear bond strength, long open time, flexibility, water immersion strength, heat aging and freeze and thaw resistance.
2. Description of Related Art
Tiles, particularly ceramic tiles and stone, are predominantly installed using thin-bed (or thin-set) mortars because significantly thinner and lighter applications of mortar, typically and approximately xe2x85x9xe2x80x3 (3 mm) to xc2xdxe2x80x3 (12 mm) can be made to set the tile.
Traditionally, tile has been installed over a substrate with a Portland cement mortar bed approximately 2xe2x80x3 (50 mm) thick to ensure sufficient moisture is present to properly hydrate the cement content and develop strength. Also referred to as the xe2x80x98conventional methodxe2x80x99 or the xe2x80x98mud methodxe2x80x99, this installation technique generally requires a separate, thin xe2x80x98bond coatxe2x80x99 or xe2x80x98slurry bond coatxe2x80x99 be applied between the tile and the surface of the thick bed mortar to provide proper adhesion. In addition, if not bonded to the underlying surface, the thick bed mortar also needs galvanized, welded steel reinforcing wire placed at its midpoint to provide tensile and flexural resistance to structural deflection. These factors make the thick bed method heavier, more material intensive, more laborious, slower and needing higher skill levels. For these reasons, thick bed installations have increasingly been replaced by thin-set and medium bed mortars that incorporate various Portland cement modifiers to improve physical performance and to allow bonding of tile to substrates with far less material.
For convenience, the following description will be directed to thin-set mortars but it will be understood to those skilled in the art that the invention also applies to mortars in general and in particular cementitious medium bed mortars, which are applied in a similar manner but at greater depth to accommodate more uneven substrates and/or tile thickness variations, and underlayments (or leveling mortars) as well as cement grouts and pointing mortars, which are used to fill the spaces between the set tiles. The term xe2x80x9ctilexe2x80x9d will be used herein to refer to other masonry products such as stone, bricks, pavers, and the like and the term xe2x80x9cmortarxe2x80x9d will be used herein to refer to thin-set mortars, medium bed mortars, underlayment or leveling mortars and grouts and pointing mortars.
Currently, most cement-based thin-set mortars, medium bed mortars, underlayments and grouts and pointing mortars contain cement, such as Portland or calcium aluminate cement, a water retention aid and sand. In addition, so called xe2x80x98multi-purposexe2x80x99 or xe2x80x98polymer modifiedxe2x80x99 mortars and grouts contain spray dried polymers that enhance physical properties, such as compressive strength, or, in the case of mortars, the ability to bond to non-masonry substrates such as exterior grade plywood.
The thin-set mortars, medium bed mortars, underlayments and grouts and pointing mortars are typically delivered to the job site in dry powder form and water or a liquid polymer such as latex is then added while mixing to produce a plastic, wet consistency. Thin-set and medium bed mortars are typically then trowelled over the substrate using a notched trowel, or similar tool, having dentations ranging in size from {fraction (3/16)}xe2x80x3 (5 mm) to xc2xexe2x80x3 (19 mm) depending on mortar and tile type. The tiles are then placed into the wet mortar, aligned with tiles already set or other reference marks and beaten in until level. Once the tiles are firmly set, the joints or spaces between them are filled with a grout mortar, typically cement-based, using a rubber float or similar device.
The above mortars and grouts for installing tile require a combination of performance properties to be commercially acceptable including high bond and shear bond strength, flexibility, water immersion strength, sag resistance, open time, heat aging and freeze and thaw resistance depending on type and application. Many mortars and grouts satisfy one or more of the above properties but it is highly desirable to provide mortar and grout products which has enhanced overall performance properties.
Sag resistance is particularly important, for mortars and grouts used for installing tile over vertical and inclined substrates. Preventing tiles from dropping down out of alignment after being placed, and reducing the slumping of grout in joints, have material effects on installation productivity, quality, profitability and, ultimately, on market acceptance. Moreover, high sag resistance in mortars is beneficial in horizontal applications involving heavy tiles, where it provides additional support against flooring units xe2x80x98sinkingxe2x80x99 and causing the common installation defect known as xe2x80x98lippagexe2x80x99. Finally, high sag resistance grouts also benefit horizontal installations in the instance where void spaces caused by inadequate bedding of tiles frequently produce xe2x80x98sinkholesxe2x80x99 in the finished grout application.
This invention is also useful in underlayments (or leveling mortars) whose primary, but not sole, functions are to prepare uneven substrates to receive tile installed by the thin or medium bed methods, to accommodate differences in tile thickness or stone xe2x80x98gaugexe2x80x99 and to improve the deflection resistance of certain substrates to a degree that permits proper support for the hard, more brittle tiles placed over them, thereby reducing the common problems of tile crazing, cracking and de-lamination. Moreover, the synergistic effects of combining the novel components of this invention produce an underlayment with superior flexural resistance, improved xe2x80x98cohesivexe2x80x99 (internal shear) strength, better workability and xe2x80x98healxe2x80x99 time, reduced water demand and the ability to be xe2x80x98placedxe2x80x99 without subsequent slumping or shrinkage. In general, a cement based underlayment powder is mixed with water to a very fluid consistency (usually 1.5-1.75 gallon of water per 50 pound bag powder). The fluid mixture is poured or pumped on the floor and a rake used to distribute the underlayment evenly and a long handle flat trowel or squeegee used to make the surface even.
It is known to incorporate finely divided inorganic fibers, for example, mineral wool, glass wool, and asbestos in hydraulic cement-based thin-set mortars for improved sag resistance as discussed in U.S. Pat. No. 4,218,258 assigned to the assignee of the present invention. Latex is also disclosed as being useful for improving shear bonding and increasing the resistance to the effects of freeze-thaw cycles. U.S. Pat. No. 4,065,319 discloses the use of inorganic and organic fibers such as asbestos, mineral wool, glass fibers, fibrous low substitution or cross linked carboxymethyl cellulose and the like to increase the sag resistance. In U.S. Pat. No. 4,402,752, it is disclosed to incorporate long-chain organic polymers such as anionic and nonionic long-chain polyacrylamide materials to improve sag resistance of the mortar. It is also noted therein that the use of clay has also been developed for use in mortars both alone and in combination with the long-chain organic polymers.
Mortars such as thin-set mortars, medium bed mortars, underlayments and grouts and pointing mortars, however, require more than sag resistance as noted above and it is a continuing goal of industry to provide such mortars having enhanced overall performance properties so that a single mortar product can be used in a variety of applications such as setting both vertical and horizontal tiles in interior as well as exterior applications.
Conventional cement-based mortars contain a cement, preferably Portland or calcium aluminate cement or other hydraulic cements, fillers such as sand, clay and calcium carbonate and a water retaining agent and sometimes a polymer to improve the sag resistance as noted above. Improving sag resistance however, usually reduces the open time of the mortar. Open time (or workability) is very important in order to obtain good bond strength and may be defined as the amount of time it takes before a dry surface or skin forms on the troweled mortar. A dry surface or skin surface can lead to poor bonding between the tile and the mortar bed. An increase in open time allows the user to spread a larger area of mortar with less chance of drying before laying the tile. Adding fiber to hydraulic cement-based mortars however generally detracts from workability and open time and in order to improve the workability and open time more water or liquid is required. Adding more liquid or water will typically make the cement base products more porous and weaker and generally reduces other performance properties of the mortar such as the bond strength, freeze and thaw properties, flexibility, and water immersion strength.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an improved mortar such as cement-based thin-set mortar, medium bed mortar, underlayment and grout and pointing mortar compositions having enhanced overall performance properties.
It is another object of the present invention to provide a method for making an improved mortar such as a cement-based thin-set mortar, medium bed mortar, underlayment and grout and pointing mortar composition and a method for using the thin-set mortar, medium bed mortar, underlayment and grout and pointing mortar of the invention.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects, which will be apparent to those skilled in art, are achieved in the present invention which relates in one aspect to an improved mortar and in particular a cement-based thin-set mortar comprising a cement, preferably a hydraulic cement such as Portland cement, and a water retaining agent, preferably a cellulose ether or an alkyl derivative of cellulose, with the improvement comprising employing in the mortar composition an effective amount of a poly (p-phenylene terephthalamide) polymer fiber (xe2x80x9cp-aramidxe2x80x9d) and/or poly(m-phenylene terephthalamide) polymer (xe2x80x9cm-aramidxe2x80x9d) to improve the overall performance properties of the mortar. A fibrillated p-aramid polymer is preferred.
In another aspect of the invention an improved medium bed mortar is provided with the improvement comprising employing in the mortar composition an effective amount of a poly (p-phenylene terephthalamide) polymer fiber (xe2x80x9cp-aramidxe2x80x9d) and/or poly(m-phenylene terephthalamide) polymer (xe2x80x9cm-aramidxe2x80x9d) to improve the overall performance properties of the mortar. A fibrillated p-aramid polymer is preferred.
In another aspect of the invention an improved underlayment (leveling mortar) is provided with the improvement comprising employing in the mortar composition an effective amount of a poly (p-phenylene terephthalamide) polymer fiber (xe2x80x9cp-aramidxe2x80x9d) and/or poly(m-phenylene terephthalamide) polymer (xe2x80x9cm-aramidxe2x80x9d) to improve the overall performance properties of the mortar. A fibrillated p-aramid polymer is preferred.
In another aspect of the invention a cement-based grout (or pointing mortar) is provided with the improvement comprising employing in the grout an effective amount of the above p-aramid and/or m-aramid fiber. A fibrillated p-aramid is likewise preferred. In general, a cement-based grout comprises cement, filler, cement accelerator, water retaining agent, defoamer and polymer.
When the mortar or agent is admixed with a liquid media, preferably water or an aqueous latex, to form a plastic and trowable wet mortar, the novel mortar of the invention can be utilized in thin and medium layers and as underlayment for setting tiles and also in grouts and pointing mortars to fill in the spaces between the set tiles.
The improved cement mortars are workable and easy to apply and are well-suited for thin-set, medium bed, underlayment and grouting applications and provide enhanced high tensile bonding and shear bonding strength, sag resistance, open time, flexibility, water immersion strength, heat aging and freeze and thaw resistance.